A conventional manner of igniting fluorescent lamps is with the use of a glow bottle starter, especially in connection with compact fluorescent lighting applications. The glow starter is turned on at a voltage much lower than the fluorescent lamp it is to start. Initially, the glow starter is in a high impedance state, as the discharge gas within it heats up. This glow discharge heat acts to heat the bimetallic strip, causing contacts to close, thereby drawing current from the external ballasting inductor. The glow discharge ceases, thereby permitting the bimetallic strip to cool, until the contacts open. When the contacts open, energy stored in the ballast inductor generates a high voltage ignition pulse across the fluorescent lamp, causing lamp ignition. Once ignition occurs, the arc current builds up and the ballast inductor limits the current to the rating of the lamp. If the ignition pulse does not start the lamp, additional ignition pulses will be generated.
A drawback with glow starters is that, repeated ignition pulses accelerate deterioration of the lamp. Further, as lamps age there are times when the fluorescent lamp may be running, the glow starter could also turn on, ruining the discharge process in the fluorescent lamp itself Consequently, extensive heating could occur causing melting or less than desirable end-of-life failures of the product.
Others have attempted to provide non-glow electronic starters. One such system is discussed in U.S. Pat. No. 5,059,870 to Choon. This patent employs a triac having a trigger electrode, and having an anode and cathode. Further implemented is a positive thermistor and a time constant circuit such as an RC circuit to form a triggering network which is coupled to a triggering electrode. When the positive thermistor is heated by current flow in the circuit so that its resistance becomes greater, the trigger angle of the triac, which is controlled by the signal produced by the time constant circuit is varied. The trigger signal causes the triac to suddenly cut off at a selected voltage below the self-maintenance current of the triac producing a reactive voltage across the fluorescent lamp. The time at which the signal occurs changes as the thermistor heats, causing the reactive voltage to increase at each cycle of the a.c. power until the reactive voltage is sufficient to turn the lamp on. A drawback to such a circuit is the use of heating within the starter circuit itself, which can decrease the life expectancy of the starter circuit. A further disadvantage is the cost of the elements to create the cited electronic circuit. Also, starters such as Choon cannot be started substantially instantaneously after it is turned off after operation. Rather, a shutdown or cooling off period will need to be provided for the heating element.
It would be desirable to provide an electronic starter, for a fluorescent lamp, which provides only a single ignition signal for each power-up of the system, in order to eliminate undesirable repeated starting attempts, as well as to eliminate inappropriate start attempts during operation of the lamp itself. It is also desirable to provide an electronic starter having an extended life span which has substantially instantaneous starting and which uses components that provide for economic benefits in the manufacturing process.